Researchers at ETH in Zurich have succeeded for the first time in building a miniature medical robot out of both metal and plastic using 3D lithography. The miniature robot structures are just a quarter of a millimetre long and can be controlled by a magnetic field in medical applications.
"Metals and polymers have different properties, and both materials offer certain advantages in building micromachines. Our goal was to benefit from all these properties simultaneously by combining the two," said Carlos Alcântara, a researcher in Salvador Pané's group at the Institute of Robotics and Intelligent Systems and one of the two lead authors of the paper.
Using magnetic fields means the micromachines must have magnetic metal parts. Polymers, in contrast, have the advantage that they can be used to construct soft, flexible components as well as parts that dissolve inside the body. If medication is embedded in this kind of soluble polymer, it is possible to selectively supply active substances to certain points in the body.
Pané’s group has been working on 3D lithography and used this method to produce a template for the micromachines. These templates have narrow grooves that serve as a "negative" and can be filled with the chosen materials.
Using electrochemical deposition, the scientists fill some of the grooves with metal and others with polymers before ultimately dissolving the template away with solvents. "Our interdisciplinary group consists of electrical engineers, mechanical engineers, chemists, and materials scientists who all work closely together. That was the key to developing this method," said Fabian Landers, other lead author of the paper in Nature Communications.
As a proof of principle for making micromachines by interlocking materials, the ETH scientists created various miniscule vehicles with plastic chassis and magnetic metal wheels powered by means of a rotating magnetic field. Some of the vehicles can be propelled across a glass surface, while others - depending on the polymer used - can float in liquid or on